ASTM F1878-98
(Guide)Standard Guide for Escort Vessel Evaluation and Selection
Standard Guide for Escort Vessel Evaluation and Selection
SCOPE
1.1 This guide covers the evaluation and selection of escort vessels that are to be used to escort ships transiting confined waters. The purpose of the escort vessel is to limit the uncontrolled movement of a ship disabled by loss of propulsion or steering to within the navigational constraints of the waterway. The various factors addressed in this guide also can be integrated into a plan for escorting a given ship in a given waterway. The selection of equipment also is addressed in this guide.
1.2 This guide can be used in performance-based analyses to evaluate:
1.2.1 the control requirement of a disabled ship,
1.2.2 the performance capabilities of escort vessels,
1.2.3 the navigational limits and fixed obstacles of a waterway,
1.2.4 the ambient conditions (wind and sea) that will impact the escort response, and
1.2.5 the maneuvering characteristics of combined disabled ship/escort vessel(s).
1.3 This guide outlines how these various factors can be integrated to form an escort plan for a specific ship or a specific waterway. It also outlines training programs and the selection of equipment for escort-related activities.
1.4 A flowchart of the overall process for developing and implementing an escort plan is shown in Fig. 1. The process begins with the collection of appropriate data, which are analyzed with respect to the performance criteria and in consultation with individuals having local specialized knowledge (such as pilots, waterway authorities, interest groups, or public/private organizations, and so forth). This yields escort vessel performance requirements for various transit speeds and conditions; these are embodied in the ship's escort plan. When the time comes to prepare for the actual transit, the plan is consulted in conjunction with forecast conditions and desired transit speed to select and dispatch the appropriate escort vessel (or combination of vessels). A pre-escort conference is conducted to ensure that all principal persons (ship master, pilot, and escort vessel masters) have a good understanding of how to make a safe transit and interact in the event of an emergency.
1.5 This guide addresses various aspects of escorting, including several performance criteria and methodologies for analyzing the criteria, as well as training, outfitting, and other escort-related considerations. This guide can be expanded as appropriate to add new criteria, incorporate "lessons learned" as more escorting experience is gained in the industry, or to include alternative methodologies for analyzing the criteria.
1.6 This guide addresses physical control of the disabled ship with the assistance of the escort vessel(s). Other possible functions, such as firefighting, piloting, or navigational redundancy, are outside the scope of this guide. Also, this guide was developed for application to oceangoing ships in coastal waterways; it is not suitable for application to barge strings in riverine environments.
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An American National Standard
Designation: F 1878 – 98
Standard Guide for
Escort Vessel Evaluation and Selection
This standard is issued under the fixed designation F 1878; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope and escort vessel masters) have a good understanding of how
to make a safe transit and interact in the event of an emergency.
1.1 This guide covers the evaluation and selection of escort
1.5 This guide addresses various aspects of escorting, in-
vessels that are to be used to escort ships transiting confined
cluding several performance criteria and methodologies for
waters. The purpose of the escort vessel is to limit the
analyzing the criteria, as well as training, outfitting, and other
uncontrolled movement of a ship disabled by loss of propulsion
escort-related considerations. This guide can be expanded as
or steering to within the navigational constraints of the
appropriate to add new criteria, incorporate“ lessons learned”
waterway. The various factors addressed in this guide also can
as more escorting experience is gained in the industry, or to
be integrated into a plan for escorting a given ship in a given
include alternative methodologies for analyzing the criteria.
waterway. The selection of equipment also is addressed in this
1.6 This guide addresses physical control of the disabled
guide.
ship with the assistance of the escort vessel(s). Other possible
1.2 This guide can be used in performance-based analyses
functions, such as firefighting, piloting, or navigational redun-
to evaluate:
dancy, are outside the scope of this guide. Also, this guide was
1.2.1 the control requirement of a disabled ship,
developed for application to oceangoing ships in coastal
1.2.2 the performance capabilities of escort vessels,
waterways; it is not suitable for application to barge strings in
1.2.3 the navigational limits and fixed obstacles of a water-
riverine environments.
way,
1.2.4 the ambient conditions (wind and sea) that will impact
2. Referenced Documents
the escort response, and
2.1 Code of Federal Regulations Document:
1.2.5 the maneuvering characteristics of combined disabled
33 CFR Part 168—Escort Vessels for Certain Tankers, Final
ship/escort vessel(s).
Rule
1.3 This guide outlines how these various factors can be
2.2 IMO Resolutions:
integrated to form an escort plan for a specific ship or a specific
IMO Resolution A.601(15)—Provision and Display of Ma-
waterway. It also outlines training programs and the selection
neuvering Information on Board Ships
of equipment for escort-related activities.
IMO Resolution A.751(18)—Interim Standards for Ship
1.4 A flowchart of the overall process for developing and
Maneuverability
implementing an escort plan is shown in Fig. 1. The process
2.3 Marine Safety Committee Circulars:
begins with the collection of appropriate data, which are
MSC Circular 389/Interim Guidelines for Estimating Ma-
analyzed with respect to the performance criteria and in
neuvering Performance in Ship Design
consultation with individuals having local specialized knowl-
MSC Circular 644/Explanatory Notes to the Interim Stan-
edge (such as pilots, waterway authorities, interest groups, or
dards for Ship Maneuverability
public/private organizations, and so forth). This yields escort
vessel performance requirements for various transit speeds and
3. Terminology
conditions; these are embodied in the ship’s escort plan. When
3.1 For purposes of clarity within this guide, the vessel
the time comes to prepare for the actual transit, the plan is
being escorted is referred to as the “ship” or “disabled ship.”
consulted in conjunction with forecast conditions and desired
The vessel accompanying the ship as its escort is referred to as
transit speed to select and dispatch the appropriate escort vessel
the “escort vessel.”
(or combination of vessels). A pre-escort conference is con-
3.2 The escorting measures addressed in this guide are
ducted to ensure that all principal persons (ship master, pilot,
based on performance.
1 2
This guide is under the jurisdiction of Committee F-25 on Ships and Marine Available from the Superintendent of Documents, U.S. Government Printing
Technology and is the direct responsibility of Subcommittee F25.06 on Marine Office, Washington, DC 20402.
Environmental Protection. Available from the International Maritime Organization, 4 Albert Embankment,
Current edition approved April 10, 1998. Published November 1998. London, SE1 7SR U.K.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 1878
FIG. 1 Flowchart of the Overall Process for Developing and Implementing an Escort Plan
3.2.1 The term “performance measure” refers to perfor- 3.3.2 Omni-Directional Propulsion System—The propulsive
mance capabilities that must be possessed by the escort thrust is steerable in any direction (360°) around the hull.
vessel(s) in controlling the disabled ship within a particular Examples are the azimuthing Z-drive screw propeller system
waterway. This requires a holistic analysis of the combined and the vertical axis cycloidal system.
maneuvering dynamics of the escort vessel(s) and ship within 3.4 The terms “direct mode” and “indirect mode” refer to
the waterway in ambient weather and sea conditions. two towing modes for exerting control forces on a disabled
Performance-based requirements involve extensive preplan- ship via towline from the escort vessel.
ning and analyses, but offer greater assurance that the escort 3.4.1 Direct Mode—The towline force is derived directly
vessel(s) actually will be effective. The methodologies and from the escort vessel’s propulsion system. In general, the
processes presented in this guide can be used in determining towline orientation is over the bow or over the stern of the
the performance envelope of an escort vessel at different transit escort vessel, and only the propulsive thrust vector parallel to
speeds and under a range of weather and sea conditions. the towline axis is effective on the disabled ship.
3.3 The terms “conventional propulsion” and“ omni- 3.4.2 Indirect Mode—The towline force is derived from the
directional propulsion” refer to propulsion systems of the escort vessel’s hull drag as it is pulled along behind the
escort vessel. disabled ship (similar to a drag chute). High-performance
3.3.1 Conventional Propulsion System—The propulsive escort vessels should have sufficient stability so that they can
thrust is fixed in a fore/aft direction. turn approximately sideways to the towline without capsizing
F 1878
(tripping), thereby substantially increasing their hull drag and, 3.6.9 maneuvering coeffıcients, n—a set of numerical coef-
consequently, increasing their towline force. The propulsion ficients the are used in polynomial representations of the forces
system of these escort vessels is used indirectly to maintain an acting on a ship in terms of the instantaneous state of the ship.
over-the-side towline orientation (rather than pull directly on 3.6.10 oppose maneuver, n—an escort vessel maneuver in
the towline itself). In the indirect mode, specially designed
which the assisting escort vessel(s) apply maximum steering
escort vessels can kite off to one side or the other of the force to a disabled ship to turn the ship against its rudder. In
disabled ship’s stern, thereby imposing substantial steering
this maneuver, the objective is to return the ship to its original
forces on the ship as well as retarding forces to slow it down. heading by opposing the rudder forces.
3.6.11 propulsion failure, n—the ship is unable to propel or
3.5 The terms “parameters” and “constraints” refer to addi-
tional conditions that define the escort scenario and response. actively stop itself.
3.6.12 response times, n—the sequence of time delays
3.5.1 Parameters—Additional details that are specified as
following a disabling failure on a transiting ship before the
part of the performance criteria to define more fully the
escort vessel(s) can apply corrective forces.
performance “problem” that must be solved by the escort
3.6.13 rescue tow, n—a maneuver in which the escort vessel
vessel(s). Parameters are used to customize the performance
makes up lines and pulls the disabled ship; undertaken after all
criteria to reflect a particular waterway or a specific perfor-
forward way has come off the disabled ship.
mance objective. Examples of parameters include an initial
ship speed at moment of failure, or winds, currents, and sea 3.6.14 retard maneuver, n—an escort vessel maneuver in
which the assisting escort vessel(s) apply maximum braking
state conditions that must be assumed during the escort
response. force to a disabled ship. In this maneuver, the objective is to
take speed off the ship as quickly as possible by pulling astern.
3.5.2 Constraints—Limitations associated with “solving”
The control of a ship’s heading is not an objective. Also
the performance problem. Examples of constraints include the
referred to as arrest.
stability limits of the escort vessel (which limit how much
3.6.15 rudder failure, n—the ship’s rudder is locked at some
towline heeling moment the escort vessel can tolerate),
angle or it is swinging uncontrollably.
strength limits of the ship’s bollards (which limit how much
3.6.16 ship track/course, n—the path covered by the ship’s
towline force can be applied), or the navigable limits of the
center of gravity during a voyage, a waterway transit, or a
waterway (which limit how much maneuvering room is avail-
maneuver.
able).
3.6.17 tactical diameter, n—the distance, perpendicular to
3.6 Definitions:
the original course direction, between the ship’s center of
3.6.1 allision, n—a collision with a fixed object.
gravity at the start and at the end of a 180° heading change.
3.6.2 allowable reach, n—the straight line distance forward
3.6.18 zigzag maneuver, n—a test used to measure the
from the designated ship, parallel to its course direction, to a
effectiveness of the rudder to initiate and check course
point at which a grounding of an allision would occur.
changes. The maneuver is described in MSC Circular 644,
3.6.3 allowable transfer, n—the straight line distance from
Section 2.2.
the designated ship, perpendicular to its course direction, to a
3.7 Evaluation and Selection Variables:
point at which a grounding or an allision would occur.
3.7.1 transit speeds, n—the speed of the escorted ship
3.6.4 assist maneuver, n—an escort vessel maneuver in
measured through the water. The transit speed takes into
which the assisting escort vessel(s) apply maximum steering
account tidal and wind-driven currents. Transit speed is not
force to a disabled ship to enhance the turn of the rudder. In this
over ground (SOG) as measured by GPS, Loran, or radar.
maneuver, the objective is to make the radius of turn of the ship
3.7.2 bollard pull, n—the maximum sustainable force that
as small as possible.
the escort vessel is able to develop while pulling on a towline
3.6.5 emergency scenarios, n—the complete description of
attached to a stationary object. The forward and astern bollard
the failure, the navigational situation, and the emergency assist
pulls are individually specified.
response.
3.7.3 dynamic pull (at a particular speed), n—the maxi-
3.6.6 escort operating area, n—a subregion of the water-
mum sustainable force that the escort vessel is able to develop
way, harbor, bay, and so forth, that has been identified as the
while moving through the water at a particular speed.
region in which the escort vessel(s) will stand by or accompany
3.7.4 transfer, n—the distance perpendicular to the original
the designated ship. The subregion may contain locations that
track that a ship’s center of gravity travels in a 90° change in
would require timely escort vessel assistance should the ship
heading.
experience a propulsion or steering failure, or both.
3.7.5 advance, n—the distance parallel to the original track
3.6.7 escort vessel, n—a vessel that is assigned to stand by
that a ship’s center of gravity travels in a 90° change of
or dedicated to travel in close proximity to a designated ship to
heading.
provide timely assistance should the ship experience a propul-
3.7.6 performance limits, n—limits of performance mea-
sion or steering failure, or both. The escort vessel has appro-
sures such that under all circumstances, the use of vessels,
priate fendering and towing gear to provide emergency assist
equipment, or crew shall not place the life and safety of
capability relative to the demand of the disabled ship.
individuals in jeopardy. No applicable federal or state regula-
3.6.8 grounding, n—impact of a ship’s hull with the sea tions should be exceeded in determining escort vessel perfor-
bottom. mance capabilities and limits.
F 1878
4. Significance and Use 4.6.3 Navigational constraint within which the disabled ship
must be brought under control (such as allowable advance and
4.1 This guide presents some methodologies to predict the
transfer, cross-track error, and so forth);
forces required to bring a disabled ship under control within the
4.6.4 Wind, current, and sea conditions; and
available limits of the waterway, taking into account local
4.6.5 Time delays, failure recognition, decision making,
influences of wind and sea conditions. Presented are method-
escort vessel notification, escort vessel positioning, achieving
ologies to determine the control forces that an escort vessel can
full power, and so forth.
reasonably be expected to impose on a disabled ship, taking
4.7 The anticipated users of this guide are:
into account the design of the ship, transit speed, winds,
4.7.1 Ship owners/operators who are required to select
currents, and sea conditions. In some instances, this guide
escort vessel(s) that meet the performance measures addressed
presents formulae that can be used directly; in other instances,
by this guide.
in which the interaction of various factors is more complicated,
4.7.2 Escort vessel designers/operators who need to evalu-
it presents analytic processes that can be used in developing
ate the performance capabilities of their vessels with respect to
computer simulations.
the measures addressed by this guide.
4.2 Unlike the more traditional work of berthing assistance
4.7.3 Regulatory agencies that have imposed the perfor-
in sheltered harbors or pulling a “dead ship” on the en
...
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